In rotor spinning devices of the above-described type, as disclosed for example in German Patent Disclosure DE 21 12 170 A1, a sliver introduced between a drawing-in cylinder and a feeding trough is unraveled by an opening cylinder to become separated into individual fibers. In the course of this process, debris particles and fibers are separated to the greatest extent possible. The opening cylinder conveys both the fibers and debris over a fiber guide surface into the area of a debris discharge opening. In the course of this transport, the fibers as well as the debris particles are rapidly accelerated by the opening cylinder itself and by the air flow circulating around the opening cylinder to approach the circumferential speed of the opening cylinder. Because of the centrifugal forces acting on them, the fibers and debris particles tend to leave the circular path tangentially as soon as the forced mechanical guidance of the fiber guide surface is interrupted, such as is the case in the area of the debris discharge opening.
For this reason, a debris collecting chamber is disposed directly underneath the debris discharge opening and is connected via a conduit with the central suction unit of the spinning machine. In addition, this debris collecting chamber has an air inlet opening which can be closed by means of a slide.
A comparable open-end spinning machine, slightly modified in the area of the debris discharge opening, is described in German Patent Publication DE 28 56 028 A1.
To prevent the spinnable fibers from being removed from the opening cylinder in the area of the debris discharge opening in addition to the debris particles, the debris discharge opening also serves as an opening for an air flow entering the opening cylinder housing. This air flow is directed onto the opening cylinder to pneumatically guide and retain the fibers against the opening cylinder due to the relatively large specific surface area of the fibers in relation to their relatively low mass. The debris particles have a relatively larger mass and, in turn, have a clearly greater kinetic energy than the fibers which thereby overcome this fiber-retaining air flow and are therefore discharged tangentially under the prevailing centrifugal force.
The discharged debris particles are subsequently entrained by a second air flow and are removed through a discharge opening. The debris chamber is disposed directly following the debris discharge opening of the opening cylinder housing and is divided into a debris separation zone and a debris removal zone by an air guiding wall disposed at a short distance from the debris discharge opening.
In this manner, it is attempted to separate the air flows which are aimed in the same direction and to remove to the greatest extent possible the mutual effect of these flows on each other.
An open-end rotor spinning device with a debris chamber disposed directly underneath the opening cylinder is also known from the later-issued German Patent Publication P 43 10 810, which has two separate air flow systems with their own respective aspirating openings. In this case an air flow system acting in the bottom area of the debris chamber removes the debris particles combed out by the opening cylinder, while a second air flow system acting in the opposite direction terminates in a suction flow which rotates along with the opening cylinder. The particular disposition of the aspirating openings achieves a more or less pronounced separation of the two air flow systems.
The debris removal at the opening cylinder housing of a rotor spinning machine constitutes an important factor in the optimal processing of fiber materials. Even though the technology of the debris removal devices appears to be relatively simple, these devices are nevertheless very difficult arrangements which react very sensitively to changes. For example, small modifications in the area of the debris discharge openings can disadvantageously change the flow conditions and therefore have considerable influence on the spinning results which are obtainable.